1. Field of Invention
The invention relates to an electric discharge controller, an electric discharge control method and its program.
2. Description of Related Art
In a vehicle drive unit mounted to an electric automobile, as an electrically operated vehicle, and generating the torque of a drive motor, i.e., drive motor torque, and transmitting the drive motor torque to a drive wheel, the drive motor is conventionally operated by receiving a direct electric current from a battery at a power applying time (driving) time, and generates the drive motor torque. At a regenerative (electricity generating) time, the drive motor receives torque by inertia of the electric automobile, and generates the direct electric current and supplies this electric current to the battery.
Further, a planetary gear unit having a sun gear, a ring gear and a carrier is arranged in a vehicle drive unit mounted to a hybrid type vehicle as the electrically operated vehicle and transmitting one portion of the torque of an engine, i.e., engine torque to an electric generator (electric generator motor) and transmitting the remaining engine torque to a drive wheel. The carrier and the engine are connected to each other. The ring gear, the drive motor and the drive wheel are connected to each other. The sun gear and the electric generator are connected to each other. Rotation outputted from the ring gear and the drive motor is transmitted to the drive wheel and the driving force is generated.
In each of the vehicle drive units, an inverter is arranged between the drive motor and a drive motor controller. The inverter is operated in accordance with a driving signal sent from the drive motor controller. The electric currents of U, V and W phases are generated by receiving the direct electric current from the battery. The electric currents of the respective phases are supplied to the drive motor, and the drive motor is driven. Further, in the hybrid type vehicle, the inverter is also arranged between the electric generator and an electric generator controller. The inverter is operated in accordance with a driving signal sent from the electric generator controller, operates the electric generator and generates the direct electric current. The direct electric current is sent to the battery and the battery is charged. The electric currents of the U, V and W phases are generated by receiving the direct electric current from the battery. The electric currents of the respective phases are supplied to the electric generator and the electric generator is operated.
Therefore, the inverter has a plurality of transistors, e.g., six transistors. Accordingly, when the driving signal is sent to each transistor in a predetermined pattern, the transistor is turned on and off, the electric currents of the respective phases are generated and the direct electric current is generated.
When the supply of the electric current from the battery to the inverter is interrupted and the driving of the drive motor is stopped, for example, when running of the electric automobile is terminated and an ignition switch is turned off, an electric charge corresponding to electrostatic capacity is accumulated in a capacitor arranged between the battery and the inverter. When a power source of the drive motor controller is turned off while the electric charge is accumulated in the capacitor, the driving signal sent to each transistor is transiently set to an un-control state. As its result, there is a case in which the transistor is turned on and a short-circuit electric current flows so that the durability of the drive motor controller is reduced.
Therefore, an electric discharge controller is provided and the capacitor is electrically discharged by the electric discharge controller. The electric discharge controller sets an electric current command value for magnetization, e.g., a d-axis electric current command value id* to nonzero (a predetermined value except for zero (0)), and also substantially sets an electric current command value for torque generation, e.g., a q-axis electric current command value iq* to zero. Thus, the drive motor is driven without generating the drive motor torque and the electric charge accumulated in the capacitor is consumed within the drive motor (e.g., see JP-A-9-70196).
Further, when the drive motor is driven, another electric discharge controller performs position non-synchronous electric current control by adding a higher harmonic wave to the d-axis electric current command value id* and the q-axis electric current command value id*. The drive motor torques are mutually canceled within the drive motor, the electric charge accumulated in the capacitor is consumed within the drive motor, and no drive motor torque is transmitted to the drive shaft (e.g., see JP-A-9-215102).